It should either not let you dash or let you dash but not show you dashing and then pull you back to the start. Maybe disable dashes during roots?
If you can dash from roots, what for is roots then?
I am pretty sure its correct mechanics of roots.
Problem is a bit deeper.
For example , if you would not be able to use any movement/dash abilities during roots - it is perfect change.
But in current state , your character just teleporting back if disable(root/stun) was casted at the same as you use your movement ability. There is almost no way how you can predict it.
So basically it is totally RNG. You will just waste your spell.
That's why SBI need to change it.